Spoiler alert: If our hero is going to save the world, he has to find the mothership, go inside it—penetrate it—usually through a small aperture, and blow it up.

Image: Edge of Tomorrow promotional image.

Spoiler alert. Spoiler alert for the new Tom Cruise flick Edge of Tomorrow, spoiler alert for the slightly older Tom Cruise flick Oblivion, and spoiler alert—for good measure, while we're at it—for a lot of Tom Cruise flicks, plus a healthy percentage of science fiction movies from the last fifty years. Spoiler alert for a trope so insidious, so completely folded into the habitual narratives of our blockbusters, that it has become all but invisible.

This is the spoiler: at the end of the movie, if he is going to save the world, our hero has to find the mothership, and he has to blow it up. He has to go inside the mothership—penetrate it—through a small aperture. Once there, he won't have much time to plant his weapon, and it's likely he'll barely make it out before a bomb explodes deep within the mothership, collapsing it from within, shooting our hero back into the world on the shockwave of a single, orgasmic shudder of fire and light.

This meta-spoiler should conjure a montage of cinematic climaxes, from the offing of the Death Star to the menacing shadow of Independence Day's mighty mothership, wide enough to block out the sun, because it is a storytelling ritual, an incantation performed ad nauseam in the dark collective multiplex of consciousness.

Independence Day's Mothership. Screenshot.

The expression "mothership" dates to pre-science fictional times. In the 19th-century whaling trade, a large ship would serve as the central hub from which a group of small, fast cutters, designed to chase and kill whales, would operate. This ship, the mother, was reserved for the processing and storage of whale meat. Such a ship is now called a "factory ship."

But the variant used almost exclusively today, in science fiction and in the popular imagination, has a very different lineage. It dates back to the first generation of UFO hysteria, which was marked by a spell of sightings in 1947 referred to as the "Great Flying Saucer Wave." The saucers of said wave were described by those who saw them in manifold ways: as discs skipping across the sky like flat stones on a pond, as platters in birdlike formation, as flying pie-plates. But it was an anonymous woman in Palmdale, California, quoted in the press describing a "mother saucer (with a) bunch of little saucers playing around it" who inadvertently defined the idiom. Mothership.

The "Mothership" has certainly mutated over the years. The contemporary usage—the trope that should be familiar to any viewers of celluloid SF—is light-years from the Palmdale woman's vision of a mama surrounded by playful flying saucer babies. Instead, it's drawn some meaning from the original whaling motherships, as well as imported structural cues from colonies of bees and ants. Now the Mothership is part queen bee, part battery pack. She controls all the power, meting out orders to the drones and fueling them with whatever mysterious alien lifeblood is the look du jour: telepathic commands, the master code, the central brain. Kill the mother, kill the hive.

On the most elemental level, a Mothership is an easy out for filmmakers, a mechanism by which the scrappy human race can vanquish insurmountable spaceborne invaders using existing technology. David and Goliath stories always hinge on the giant's central weakness; as he can be beaned in the forehead with a rock, so can an alien fleet be downed instantly with a straight shot to the core. When a mother is killed, in life as in science fiction, it destabilizes the system—robs it of a slow-moving port, mind, home, and family. It also prevents the enemy from reproducing itself, the strategic advantage of the female.

Killing the mothership is standard operating procedure in alien invasion films: in Independence Day, the mothership must be hacked to deactivate the shields of all the defensive fighters. In Oblivion, Tom Cruise must enter and neutralize the Tet, an alien artificial intelligence with a soothing maternal voice that goes by the name of Sally.

In Edge of Tomorrow (again, spoilers) it's more of the same: an "Omega," the primary source of the alien power, characterized almost immediately as a "she," must be entered and destroyed from within.

Why not fatherships? In a largely patriarchal world, and in a genre traditionally dominated by male authors and consumers, why is the predominant image of alien power feminized? Well, obviously, aliens have always stood for the "Other." They are placeholders for the inscrutable, for all those things about women (and for other races, nations, gender assignations, ideologies, too) which are frightening to the readership. Women are a secret power. It makes sense, then, that the summit of Otherness, its military-industrial peak, would be that symbolic apex of womanhood: the Mother. Killing her destroys the alien's capacity to reproduce—the one thing men alone can't do.

Science fiction was born from a generation of pulp publishing and popular mechanics magazines marketed to young men, filled with young men's fantasies of hapless damsels and big steely rockets. Although the great feminist science fiction authors of the mid-1970s—Joanna Russ, Octavia Butler, Ursula K. LeGuin, James Tiptree, and the critic Donna Haraway, whose "Cyborg Manifesto" is a foundational document for yours truly—did much to rearrange this boy's club, creating matriarchal laboratories in the cosmos, it remains largely subversive to worldbuild outside of the patriarchy.

Which is why we usually take the mothership for granted. What is alien is Other, and what is Other is certainly not male—these are transparent truths, as elemental to science fiction cinema as three-act structure, symptoms of the assumptions we make about ourselves. Again and again, Tom Cruise blows up a womb and saves the world.

Some science fiction films employ a computational variant on the mothership idea. Instead of a massive craft, a cosmic aircraft carrier hanging in the void, the mothership is a central intelligence system: like the Tet, Elysium's core computer, the Terminator franchise's indomitable Skynet, or the "Brain Bug" from Starship Troopers, the most vaginal alien life-form in the entire universe. If it has a voice, like Siri or Cortana, it's female. "I'm in!" pronounces the hacker who bests her.

In this context, the mothership is the central node of a network. The effect of downing her is like knocking the cloud offline: all the agents, every connected device or entity, is simultaneously robbed of its brain. A million dead drones fall from the sky, clunk-clunk. Which is to say, if we have a mothership among us today, it's the Internet.

Unlike the motherships and maternal networks of science fiction, being imploded at every turn by myriad Tom Cruises—those atavistic male heroes—we wouldn't immediately die if it took a hit, but we'd certainly be weakened, sent wheeling out into the void with nothing left to conquer. Something to consider as we wade through the briar of net neutrality, as the powers that be try their hardest to infiltrate the mothership and plant bombs within her. No spoilers.